The present invention relates to a noise-canceling pickup with an electret. Especially, the present invention relates to the first-order pressure gradient air-conduction noise canceling pickup with only one electret, in which the distance between the opposite front and rear sound passing holes can be made smaller.
As those skilled in the art know, there are many conventional the first-order or the second-order pressure gradient air-conduction noise canceling pickups with the so called heart shape directional performance (cardioid microphone) or figure xe2x80x9c8xe2x80x9d type directional performance (bidirectional microphone). In the prior art, different pickups have different performances. Nevertheless, the moving-coil or the electromagnetic-type air-conduction noise canceling pickups have a relatively low sensitivity. The only way to obtain the required sound pressure is to increase the distance between the opposite front and rear sound passing holes, resulting in the distance between the opposite front and rear sound passing holes becoming too long. Furthermore, although the distance between the opposite front and rear sound passing holes can be made smaller, such as a few millimeters, with benefits that the higher sensitivity is realized for the conventional noise-canceling pickup with the electret, the distance between the opposite front and rear sound passing holes can not be made more smaller with the limit of the inner structure of the pickup. Even the desired specifications of a single pickup are realized according to the test results, when the pickup is inserted into its housing to be used as a practical microphone, the distance between the opposite front and rear sound passing holes of the microphone cylinder becomes longer, resulting in a much lower effect to cancel the noises. Especially, the effect to cancel the noises becomes much poor in the higher frequency band. With this reason, the conventional noise-canceling microphone can only be used in the case of the ambient noise being relatively low and being in the lower frequency band. In this case, the output voice is not clear enough, and the noise can not be canceled totally. As the signal-noise ratio between the practical ambient noise and the voice source is relatively low, the ambient noise usually interferes the voice output from the voice source.
In the conventional noise canceling pickups, a sound filtering layer is additionally provided on the outer surface of the end of the pickups for receiving voice from the main voice source, in order to lower the influence to the voice receiving effect of the pickups by the speaker when he/she is speaking and breathing. However, the sound filtering layer has a certain thickness, so that when mounted into the housing, the distance between the opposite front and rear sound passing holes has to be further lengthened, resulting in a much lower effect to cancel the noises. Moreover, if the pickup is not provided any outer housing of the microphone, as the sound filtering layer is made of loose material, the sound filtering layer is very easy to be damaged. The preferred structure of the noise canceling pickup is that the acoustic arrangements/performances on the two sides of the oscillating membrane are substantially symmetrical to each other. However, as the membrane tightening ring is an essential member and must be used, it is very difficult to provide a noise canceling pickup whose acoustic arrangements/performances on the two sides of the oscillating membrane are substantially symmetrical to each other.
Moreover, in the case of the voice being identified by the computer, the voice input work must be done in the special language laboratory. When used in the communication device, the only way used to cancel the noise is to make the sensitive low. Therefore, it is absolutely necessary to provide a noise canceling pickup with an electret which can cancel the noises even in the higher frequency band.
To overcome the drawbacks mentioned above, the object of the present invention is to provide a noise canceling pickup with an electret, which can be used in the higher frequency band and in a wide frequency range to cancel the noises more effectively.
According to the present invention, a noise canceling pickup with an electret is provided with a cylinder body having a front cover and a rear cover, said front cover is provided with sound passing holes, said cylinder body is provided with an oscillating membrane of the electret, a back electrode sheet and a back electrode base, wherein said cylinder body is composed of a front cylinder body and a rear cylinder body, said oscillating membrane is provided into said front cylinder body, said rear cover of said cylinder body is provided with at least one sound passing hole, and said rear cover is provided with electric elements therein.
With the arrangement according to the present invention, the distance between the opposite front and rear sound passing holes becomes shortened, therefore, a good effect of noise canceling with directional performance can be obtained, a higher signal-noise ratio can be realized, and the noise canceling pickup with an electret can be mounted onto its external supports without the outer shell.
Preferably, the membrane tightening ring is provided to abut against the oscillating membrane so as to adjust the position of the oscillating membrane.
Preferably, a damping membrane is provided within said front cylinder body to abut against the front cover thereof, said damping membrane is fixed by a damping membrane pressing sheet, and another damping membrane is provided within said front cylinder body to abut against the rear cover wall thereof.
Preferably, said damping membrane is arranged in the middle position of said front cylinder body.
Preferably, said damping membrane is arranged within said front cylinder body to abut against the rear cover wall thereof.
Preferably, the cross section of said rear cylinder body is different to that of said front cylinder body, and the connection portion between the rear cylinder body and the front cylinder body is formed so as to not prevent the sound wave from entering the rear wall sound passing holes of the front cylinder body.
Preferably, said rear cylinder body is connected to the back surface or side surface of said front cylinder body.
Preferably, said rear cylinder body is combined with a front body and a rear body, and a certain angle is arranged between the orientation of said front body and that of said rear body.
Preferably, said back electrode is output from a side wall of said front cylinder body.
Preferably, further comprising a fixing in place means which is provided on said rear cylinder body.
Preferably, said front cylinder body is provided with a partition washer which is in engagement with the damping membrane pressing sheet, a side-front washer which is in engagement with the membrane tightening ring, and a partition which is convex in the central portion thereof and is provided between said partition washer and said side-front washer, said central portion of the partition is arranged to convex to the oscillating membrane and to be projected into the membrane tightening ring, so as to form a chamber together with the oscillating membrane, and the outer surface of said convex portion is arranged to abut against the inner surface of said side-front washer and the inner surface of said membrane tightening ring.
Preferably, said front cylinder body is provided with a side-front washer which is in engagement with the membrane tightening ring, and a membrane tightening ring which is arranged between and is in engagement with said side-front washer and the oscillating membrane, wherein the membrane tightening ring is provided with a concave portion in the central portion thereof, and a chamber is formed between the concave portion and the oscillating membrane.
In a word, with the arrangement according to the present invention, the distance between the opposite front and rear sound passing holes becomes shortened, therefore, a good effect of noise canceling with the so called heart shape directional performance or figure xe2x80x9c8xe2x80x9d type directional performance can be realized, a higher signal-noise ratio can be obtained, and the noise canceling pickup with an electret can be mounted onto its external supports without the outer shell.
Above and further objects and advantages will be more easily understood from the following detailed description of the preferred embodiments taken together with the accompany drawings.